Sip协议(三)- 通话接听流程

# Sip协议(三)- 通话接听流程

本文主要记录下sip通信下接听的流程.

### 一: 接听流程

1. agent接听电话

2. 远端在未接听情况下主动挂断电话.

接听流程涉及到的请求有: INVITE,CANCEL,ACK,BYE

具体的过程如下:

### 二: sip过程

1. agent收到INVITE

```

INVITE sip:1000@10.0.0.1:10000;transport=tcp SIP/2.0

Via: SIP/2.0/TCP 10.0.0.1:5060;branch=z9hG4bKxxxx;rport=5060

Route: <sip:1000@124.64.0.1:10988>;transport=tcp

Max-Forwards: 70

From: "Extension 1001" <sip:1001@172.17.0.1>;tag=Q79QQcg41UBpe

To: <sip:1000@10.0.0.1:10000;transport=tcp>

Call-ID: e040d830-a8aa-123d-0a8e-11111111111b

CSeq: 84836083 INVITE

Contact: <sip:mod_sofia@10.0.0.1:5060;transport=tcp>

User-Agent: FreeSWITCH-mod_sofia/1.10.10-release~64bit

Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE

Supported: path, replaces

Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer

Content-Type: application/sdp

Content-Disposition: session

Content-Length: 426

X-voice_call_number: 18300000000

X-empolyee_id: 1001

X-FS-Support: update_display,send_info

Remote-Party-ID: "Extension 1001" <sip:1001@172.17.0.1>;party=calling;screen=yes;privacy=off

v=0

o=FreeSWITCH 1718762975 1718762976 IN IP4 10.0.0.1

s=FreeSWITCH

c=IN IP4 10.0.0.1

t=0 0

m=audio 16776 RTP/AVP 9 0 8 101

a=rtpmap:9 G722/8000

a=rtpmap:0 PCMU/8000

a=rtpmap:8 PCMA/8000

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15

a=ptime:20

m=video 16862 RTP/AVP 102

b=AS:3072

a=rtpmap:102 VP8/90000

a=rtcp-fb:102 ccm fir

a=rtcp-fb:102 ccm tmmbr

a=rtcp-fb:102 nack

a=rtcp-fb:102 nack pli

```

2. agent发起 Trying 100

```

SIP/2.0 100 Trying

Via: SIP/2.0/TCP 10.0.0.1:5060;branch=z9hG4bK1111;rport=5060

To: <sip:1000@10.0.0.1:10000;transport=tcp>

From: "Extension 1001" <sip:1001@172.17.0.1>;tag=027KZHpcBFDXH

Call-ID: 42ed1f48-a8ac-123d-0a8e-11111111111a

CSeq: 84836381 INVITE

Server: AgentTest/1.0.0/V2318A

Content-Length: 0

```

3. agent发起请求 Ringing 180

180: 振铃中.

```

SIP/2.0 180 Ringing

Via: SIP/2.0/TCP 10.0.0.1:5060;branch=z9hG4bKgvtvc29HgQZ5e;rport=5060

To: <sip:1000@10.0.0.1:10000;transport=tcp>;tag=ec6c9cb5b93df28e

From: "Extension 1001" <sip:1001@172.17.0.1>;tag=027KZHpcBFDXH

Call-ID: 42ed1f48-a8ac-123d-0a8e-11111111111a

CSeq: 84836381 INVITE

Server: AgentTest/1.0.0/V2318A

Content-Length: 204

Content-Type: application/sdp

v=0

o=1000@10.0.0.1 0 0 IN IP4 10.239.19.29

s=Session SIP/SDP

c=IN IP4 10.239.19.29

t=0 0

m=audio 21000 RTP/AVP 8 101

a=rtpmap:8 PCMA/8000

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15

```

4. agent接收到CANCEL请求

```

CANCEL sip:1000@10.0.0.1:10000;transport=tcp SIP/2.0

Via: SIP/2.0/TCP 10.0.0.1:5060;branch=z9hG4bKgvtvc29HgQZ5e;rport=5060

Route: <sip:1000@124.64.22.13:10988>;transport=tcp

Max-Forwards: 70

From: "Extension 1001" <sip:1001@172.17.0.1>;tag=027KZHpcBFDXH

To: <sip:1000@10.0.0.1:10000;transport=tcp>

Call-ID: 42ed1f48-a8ac-123d-0a8e-11111111111a

CSeq: 84836381 CANCEL

Reason: SIP;cause=487;text="ORIGINATOR_CANCEL"

Content-Length: 0

```

5. agent回执 200

```

SIP/2.0 200 OK

Via: SIP/2.0/TCP 10.0.0.1:5060;branch=z9hG4bKgvtvc29HgQZ5e;rport=5060

To: <sip:1000@10.0.0.1:10000;transport=tcp>

From: "Extension 1001" <sip:1001@172.17.0.1>;tag=027KZHpcBFDXH

Call-ID: 42ed1f48-a8ac-123d-0a8e-11111111111a

CSeq: 84836381 CANCEL

Server: AgentTest/1.0.0/V2318A

Content-Length: 0

```

6. agent回执487

487: Request Terminated 请求被BYE或者CANCEL所终止.

```

SIP/2.0 487 Request Terminated

Via: SIP/2.0/TCP 10.0.0.1:5060;branch=z9hG4bKgvtvc29HgQZ5e;rport=5060

To: <sip:1000@10.0.0.1:10000;transport=tcp>

From: "Extension 1001" <sip:1001@172.17.0.1>;tag=027KZHpcBFDXH

Call-ID: 42ed1f48-a8ac-123d-0a8e-11111111111a

CSeq: 84836381 INVITE

Server: AgentTest/1.0.0/V2318A

Content-Length: 0

```